Why did the convention replaced the caucus ?

Because the caucus limited participation of party members.

Due to the weakness of Federalists leadership

Explanation:

In 1820 Monroe's re-election campaign went unopposed because the Federalists had become extremely weak at the national level and no Democratic-Republican challenged Monroe which made Monroe the only presidential candidate. So with the weakness of Federalists powers and representations, after 1824, the Democratic-Republican Party broke between supporters of Andrew Jackson and supporters of Adams and both candidates condemned the caucus system. Therefore from 1831 onward, the Congressional nominating caucus was replaced with national presidential nominating conventions.

deists, human beings can know god only via reason and the observation of nature, but not by revelation or by supernatural manifestations

hope this

the noble might have thought that the system was far because they had lot of things and riches and the serf would have thought that the feudal system was un fair because of the way they were treated.